As shown in FIG. 1, a common fixture in a commercial kitchen is a spray valve 10 on the end of a flexible hose 11 that is connected to a vertical riser 12, especially as part of a pre-rinse unit of a dishwasher line. The spray valve 10 has a lever 13 for manual operation to open and close the valve 10. U.S. Pat. Nos. 2,971,520 and 5,624,074 describe a couple of examples. A common annoyance with conventional spray valves is a chattering noise and accompanying choppy flow of water that results when the valve is nearly closed.
Most of the conventional spray valves employ valve springs that bias the valve stem in a direction that is parallel to the flow of water through the valve. In most conventional spray valves, the flow of water tends to exert a force on the spring in the opposing direction (along the same axis) that the spring exerts the biasing force on the valve stem in the closed position. When the combined forces of the flowing water and the opposing spring in one of these conventional spray valves vibrates the system at the natural frequency of the valve, chatter of the valve results, and water tends to be ejected from the valve in spurts. Moreover, this chatter tends to reverberate through the connecting pipes that bring the water to the spray valve. Designers of conventional spray valves try to prevent such chatter by raising the natural frequency of the spray valve. The elevation of the conventional spray valve's natural frequency is often accomplished by providing a biasing spring with a much higher force constant. However, the increased force constant imposes an additional force requirement on the user in order to press the valve trigger to open the valve to the flow of water. The spring force is applied in opposition to the user's hand that squeezes the valve's trigger against the body of the valve in order to open the valve. The typical force that is required to be applied against the valve trigger to open a conventional spray valve is on the order of three to five pounds at the user interface.
In order to prevent back-siphonage of dirty water from a dishwashing sink under certain conditions, it is necessary to include a back-flow prevention device upstream of the conventional spray valve (either within the base faucet or a separate component disposed in the flow path between the flexible hose and the spray valve or between the rigid riser and the hose or between the base faucet and the rigid riser). Installations that fail to include at the time of installation such a separate back-flow prevention device will suffer from the aforementioned condition at a later date. There are hand held shower heads that include a check valve in the flow conduit that passes through the handle of the shower head, where the check valve is positioned upstream from the shower head and upstream from the valve.
For rinsing dirty dishes for example, the spray valve desirably produces a spray pattern with approximately twenty or so parallel streams. For washing down kitchen floors and walls, the spray valve desirably produces a spray pattern with a single high-velocity jet. When it is desired to conserve water usage, the spray valve desirably produces a low-flow spray pattern. In a conventional spray valve, changing from one spray pattern to another requires installation of a spray face with the appropriate spray pattern. In some conventional spray valves, this often requires removal of a screw that is centrally located on the spray face or removal of another separate retention device or changing out a sub-assembly of or the entire spray valve assembly. The installation thus may require special tools or partial disassembly of some of the components of the device in order to effect the installation.
For washing down kitchen floors and walls, the spray valve must be held in the open valve position for an extended period of time while the water is used to wash down the floor. The operator's hand can become fatigued from the need to apply constant pressure to maintain the spray valve in the open position. In conventional spray valves, a ring is sometimes provided on the body of the valve. The operator can slip this ring over the valve trigger of the valve to hold the valve trigger against the body of the valve and thereby maintain the valve in the open position. However, placement of the ring usually requires using both of the operator's hands. Moreover, during the placement of the ring, the direction of the valve's spray easily can be inadvertently directed where the water is unwanted. Other spray valve versions include a one-handed operable trigger lock—which is a U-shaped loop of stiff wire, such as spring steel wire, that has the two open ends of the wire pivotally mounted near the free end of the valve trigger. When the loop is not in use to engage the free end of the valve trigger to hold the valve trigger in the open valve state, the side legs of the loop are held in a detent formed in the handle. A significant exertion of force by the operator's thumb is required to snap the side legs out of the grasp of the detent to move the loop into position to hold the valve trigger in the open valve state or to snap the side legs into the grasp of the detent in order to restrain the loop in the position to allow the valve trigger to move into a position where the valve is closed.
The hot water that runs through the spray valve typically has a temperature of about 140 degrees Fahrenheit. In a conventional spray valve, the user's hand is positioned typically in close proximity to two relatively large metal (brass) masses that quickly absorb heat from the hot water. Contact temperatures above 105 degrees Fahrenheit typically would be deemed uncomfortable to the user. However, the construction of conventional spray valves attempts to solve this problem by providing air gaps between the water's flow conduit and the actual grip on the spray valve. This solution is not effective to prevent the user from coming into contact with the two relatively large metal masses that are disposed on opposite ends of the grip.
The grip portion of conventional spray valves typically is made of relatively brittle plastic that easily can crack if dropped on the edge of a sink for example. Replacing the grip requires special tools and disassembly. Leaving a broken grip endangers the hand of the user during subsequent use. Some spray valves attempt to solve this problem by providing a grip portion composed of rubber or polyurethane.
The trigger portion of a spray valve is typically equipped with a motion-limiting device to prevent the trigger from falling/moving too far from the intended activation range. This motion-limiting device or the trigger itself is susceptible to damage and one or both often becomes damaged with the passage of time.